U.S. patent number 10,330,746 [Application Number 14/435,722] was granted by the patent office on 2019-06-25 for method and device for measuring a magnetic field.
This patent grant is currently assigned to Halliburton Energy Services, Inc.. The grantee listed for this patent is Halliburton Energy Services, Inc.. Invention is credited to Li Gao, Michael T. Pelletier, David L. Perkins.
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United States Patent |
10,330,746 |
Gao , et al. |
June 25, 2019 |
Method and device for measuring a magnetic field
Abstract
A system, method, and magnetic field sensor. The magnetic field
sensor includes a strain gauge. The magnetic field sensor further
includes one or more magnetostrictive layers disposed upon the
strain gauge. The magnetostrictive layers are configured to cause a
displacement of the strain gauge in response to sensing a magnetic
field. The magnetic field sensor further includes logic connected
to the strain gauge configured to determine a parameter of the
magnetic field in response to sensing the magnetic field.
Inventors: |
Gao; Li (Katy, TX), Perkins;
David L. (The Woodlands, TX), Pelletier; Michael T.
(Houston, TX) |
Applicant: |
Name |
City |
State |
Country |
Type |
Halliburton Energy Services, Inc. |
Houston |
TX |
US |
|
|
Assignee: |
Halliburton Energy Services,
Inc. (Houston, TX)
|
Family
ID: |
53493819 |
Appl.
No.: |
14/435,722 |
Filed: |
December 31, 2013 |
PCT
Filed: |
December 31, 2013 |
PCT No.: |
PCT/US2013/078484 |
371(c)(1),(2),(4) Date: |
April 14, 2015 |
PCT
Pub. No.: |
WO2015/102616 |
PCT
Pub. Date: |
July 09, 2015 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20150268313 A1 |
Sep 24, 2015 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01V
3/26 (20130101); E21B 47/092 (20200501); G01R
33/091 (20130101); G01V 3/40 (20130101); G01R
33/18 (20130101); G01R 33/063 (20130101) |
Current International
Class: |
G01R
33/09 (20060101); G01V 3/40 (20060101); G01V
3/26 (20060101); G01R 33/06 (20060101); E21B
47/09 (20120101); G01R 33/18 (20060101) |
Field of
Search: |
;73/774,779 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2005338031 |
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Dec 2005 |
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JP |
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9915281 |
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Apr 1999 |
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WO |
|
Other References
International Search Report and Written Opinion of PCT Application
No. PCT/US2013/078484 dated Sep. 24, 2014: pp. 1-16. cited by
applicant.
|
Primary Examiner: Schmitt; Benjamin R
Attorney, Agent or Firm: Chamberlain Hrdlicka
Claims
What is claimed:
1. A magnetic field sensor, comprising: three strain gauges,
wherein each strain gauge is orthogonally positioned to the other
strain gauges, and each strain gauge comprises a vibrating
component; a coil positioned to produce a bias field to enhance
sensitivity of the strain gauges; one or more magnetostrictive
layers disposed upon each of the vibrating components of the strain
gauges, wherein the magnetostrictive layers are configured to cause
a displacement of the strain gauge in response to sensing a
magnetic field; a processor connected to the strain gauges and
configured to determine one or more parameters of the magnetic
field in response to sensing the magnetic field by measuring a
resonance frequency of the vibrating components and a difference
between the resonance frequencies of each pair of the strain
gauges.
2. The magnetic field sensor according to claim 1, further
comprising a memory configured to store readings from the strain
gauge.
3. The magnetic field sensor according to claim 1, wherein each
strain gauge includes a quartz crystal.
4. The magnetic field sensor according to claim 1, wherein the
magnetostrictive layers are formed from Terfenol-D.
5. The magnetic field sensor according to claim 1, wherein the one
or more parameters include at least an amplitude and an orientation
of the magnetic field.
6. The magnetic field sensor according to claim 1, wherein the one
or more magnetostrictive layers are deposited on each strain gauge
utilizing chemical vapor deposition.
7. The magnetic field sensor according to claim 1, wherein the one
or more parameters include an amplitude and an orientation of one
or more magnetic fields including the magnetic field and are
communicated to a remote device.
8. The magnetic field sensor according to claim 1, wherein each
strain gauge includes a plurality of gauge layers interlayered with
the one or more layers of magnetostrictive layers.
9. The magnetic field sensor according to claim 1, wherein the
magnetic field sensor is integrated in a down hole tool for natural
resource exploration.
10. The magnetic field sensor of claim 1, comprising a Helmholtz
coil configured to generate the bias field.
Description
BACKGROUND
Sensory processes for determining proximity to magnetic fields or
magnetic anomalies have improved significantly in recent years. For
example, during natural resource exploration and development sensor
measurements may be utilized to intercept various devices or
components, determine capacity, make predictions, and implement
exploration actions. In some cases, making measurements may require
bulky sensor devices that are expensive and complicated.
BRIEF DESCRIPTION OF THE DRAWINGS
Illustrative embodiments of the present invention are described in
detail below with reference to the attached drawing figures, which
are incorporated by reference herein and wherein:
FIG. 1 is a schematic representation, with a portion shown in cross
section, of a wireline logging environment in accordance with an
illustrative embodiment;
FIG. 2 is a schematic, exploded view of a magnetic field sensor in
accordance with an illustrative embodiment;
FIG. 3 is a schematic, exploded view of a magnetic field sensor in
accordance with an illustrative embodiment;
FIG. 4 is a graphical representation of a butterfly curve for a
magnetostrictive material in accordance with an illustrative
embodiment;
FIG. 5 is a schematic, representation of a magnetic field sensor
array in accordance with an illustrative embodiment;
FIG. 6 is a schematic, representation of vectors associated with
the magnetic field sensor array of FIG. 5 in accordance with an
illustrative embodiment;
FIG. 7 is a graphical representation of magnetostriction in
accordance with an illustrative embodiment;
FIG. 8 is a schematic, representation of magnetic fields sensed by
a magnetic sensor in accordance with an illustrative embodiment;
and
FIG. 9 is a graphical representation of a response by a magnetic
field sensor to a magnetic field.
DETAILED DESCRIPTION OF THE DRAWINGS
The illustrative embodiments provide a system, method, device, and
magnetic field sensor for detecting magnetic fields. In one
embodiment, a sensor may be configured to determine a magnitude and
orientation of local magnetic fields utilizing geomagnetism. The
magnetic field may be utilized for well or component interception,
formation analysis, logging, or any number of other measurement,
detection, or analysis processes.
In one embodiment, a pressure or strain gauge may be coated with
one or more layers of magnetostrictive materials. Magnetostrictive
materials are materials that change shape or dimensions in the
presence of a magnetic field. For example, the strain gauge may be
a crystal pressure gauge and the magnetostrictive material may be
Terfenol-D. However, the strain gauge may be layered, coated, or
formed from any number of magnetostrictive materials, alloys,
composites, or so forth. As a result, the materials coated,
layered, or integrated with the gauge component may be configured
to sense the changes in the magnetic field. As used herein, the
term "or" does not require mutual exclusivity.
In one embodiment, the sensed magnetic field or corresponding
changes may be converted into a frequency or signal detected by the
gauge portion of the magnetic field sensor. The magnetic field
sensor may include logic, circuitry, and so forth for converting
the signal generated by the magnetic field sensor into an analog,
digital, or visual output. In another embodiment, the detected
signal may be communicated or output to one or more connected
devices for processing and analysis.
FIG. 1 is a schematic, representation of a wireline logging
environment 100 in accordance with an illustrative embodiment. The
wireline logging environment 100 may include a number of tools,
devices, locations, systems, and equipment that may be utilized to
provide the sensor tools, systems, and methods herein described.
The wireline logging environment 100 may also include a reservoir
101.
The reservoir 101 is a designated area, location, or
three-dimensional space that may include natural resources, such as
crude oil, natural gas, or other hydrocarbons. The illustrative
embodiments may utilize sensors to determine the presence of
magnetic fields in the reservoir 101. For example, the magnetic
fields may be measured based on properties of the reservoir 101,
structures or formations, deposits, downhole tools or components,
or other materials that emanate, or perturb, a magnetic field.
Processing or computations utilizing the signals retrieved by a
magnetic field sensor may be performed downhole, on-site, off-site,
at a movable location, at a headquarters, utilizing fixed
computational devices, or utilizing wireless devices.
The reservoir may be penetrated by a wellbore 103. The reservoir
101 may include any number of formations, surface conditions,
environments, structures, or compositions. In addition to
exploration and natural resource retrieval, the wellbore 103 may be
utilized to perform measurements, analysis, or production of the
reservoir 101. The wellbore 103 may be drilled into the reservoir
101 to extract wellbore fluids or gases from the formation. The
size, shape, direction, and depth of the wellbore 103 may vary
based on the conditions and estimated natural resources available.
The wellbore 103 may include any number of support structures or
materials, divergent paths, surface equipment, or so forth.
In one embodiment, the processes herein described may be performed
utilizing specialized sensor tools, including, without limitation,
sensors, logic, circuits, interconnects, power sources, telemetry
systems, and other similar electrical components. The logic of the
sensor tools may include processors, memories, field programmable
gate arrays (FPGAs), batteries, amplifiers, application specific
integrated circuits, computer instructions, code, programs, or
applications, or any combination of software, hardware, and
firmware.
In one embodiment, the wireline logging environment 100 may include
one or more of a network 102, a wireless network 104, a facility
106, a personal computer 108, a management system 110, servers 112
and 114, a database 116, a tablet 118, a wireless device 120, a
laptop 122, and a mobile computing system 124. The mobile computing
system 124 may include downhole equipment 126 and tool 128.
The network 102 may be any type of computing or communications
network including one or more of the following networks: a wide
area network, a local area network, one or more private networks,
the Internet or public networks, a telephone network (e.g.,
publicly switched telephone network), a cable network, a satellite
network, one or more cellular networks, cloud networks, virtual
networks, and other wireless and data networks.
The wireless network 104 is one example of a wireless network for
regional or local communications (e.g., WiFi, 4G, LTE, PCS,
Bluetooth, Zigbee, WiMAX, GPRS, etc.). The network 102 and the
wireless network 104 may include any number of network nodes,
devices, systems, equipment, and components (not depicted), such as
routers, servers, network access points/gateways, cards, lines,
wires, switches, DNS servers, proxy servers, web servers, and other
network nodes and devices for assisting in routing and computation
of data/communications as herein described.
In one embodiment, integrated or external components of the mobile
computing system 124 may be configured to penetrate an earth
formation through the wellbore 103 to stimulate, energize, and
measure parameters of a formation. One or more sensors or logging
tools (e.g., probes, drill string measurement devices, nuclear
magnetic resonance imagers, etc.) may be integrated with or
connected to the download equipment 126 and tool 128 communicating
with the mobile computing system 124 to perform measurements,
logging, data retrieval, data storage, processing, and information
display.
For example, the mobile computing system 124 may determine any
number of static and dynamic properties of the reservoir 101. The
static and dynamic properties may include measurements of or
changes in pressure, depth, temperature, composition (e.g.,
hydrocarbon composition levels, measurements, and statistics),
fluid flow rate, fluid composition, density, porosity, position and
displacement, depth, and so forth. Changes or variations in the
magnetic fields present within the reservoir 101 may be utilized to
make any number of determinations regarding the natural formations,
structures, or man-made components within the reservoir 101.
The tool 128 may represent any number of logging, wireline,
slickline, measurement-while-drilling (MWD), seismic-while-drilling
(SWD), logging-while-drilling (LWD) tools, or other downhole or
reservoir tools. In one embodiment, the tool 128 may rotate sensors
to enhance measurements made by the tool 128. The tool 128 may
store or communicate the measured signals to determine magnetic
fields in each section of the reservoir 101 or the wellbore 103.
The tool 128 may be self-contained and powered or connected to one
or more fixed or mobile stations, systems, devices, equipment, or
vehicles at the surface.
For example, although not shown in FIG. 1, the wireline logging
environment 100 may alternatively be replaced by a drilling
configuration including one or more of a derrick, a hoist, pumps,
hoses, connectors, a drill string, drilling motors (e.g. top drive,
downhole motor, etc.) and other similar components (not shown). In
one embodiment, the tool 128, systems, and components described in
the illustrative embodiments may be implemented in a bottomhole
assembly (i.e., the lowermost party of the drill string) or other
portion of the drill string or exploration system and components.
As a result, the tool 128 may be utilized while drilling to detect
magnetic fields.
In one embodiment, the tool 128 or other portions of the mobile
computing system 124 may communicate one or more signals or waves
to excite magnetic fields within the reservoir 101. The wave or
signal utilized by the tool 128 to perform measurements may be
generated by the tool 128 or received from any number of sources.
In one embodiment, the waves may be generated by an electromagnetic
pulse generator or continuous wave electromagnetic source.
The personal computer 108, tablet 118, wireless device 120, laptop
122, and mobile computing system 124 may execute a local program or
app to configure the tool 128 and retrieve and utilize the
measurements acquired in the process herein described. For example,
the wireless device 120 may be configured to increase or decrease a
bias or offset field utilized by the tool 128. The wireless device
120 may also be utilized to filter particular types of signals,
turn the tool (in any of three dimensions), or so forth.
In another embodiment, the tool computations and analysis may be
performed by the management system 110, servers 112 and 114, or
other network devices. For example, the user may submit information
and parameters utilizing the wireless device 120 to perform the
calculations on the server 112 with the results being stored in the
database 116 for subsequent access. The database 116 may store the
sensor orientation information, measurements, static properties,
dynamic properties, flow simulation results (e.g., initial values,
partial output, and completed output), parameters, configuration,
settings, and so forth. The database 116 may be accessed by any
number of users and devices in the wireline logging environment 100
to retrieve and update the data.
Turning now to FIGS. 2-3 illustrative a magnetic field sensor 200
in accordance with an illustrative embodiment. The magnetic field
sensor 200 may utilize any number of configurations or embodiments.
In one embodiment, the magnetic field sensor 200 may include
multiple layers 202, 204, and 206. In one embodiment, the layer 204
represents a quartz crystal gauge or beam with fixed ends coated
with a magnetostrictive material 208 shown by layers 202 and
206.
In other embodiments, the layer may include or define a vibrating
rod or wire positioned between fixed ends coated with the
magnetostrictive materials. In addition, to having fixed ends, the
layer 204 may be cantilevered where one end of the vibrating
component is free or unfixed.
For example, the quartz crystal gauge may represent a singular
component and configuration or may define multiple components, such
as a beam, isolator mass, isolator spring, anchors or based
components, or so forth. In one embodiment, the magnetostrictive
material is Terfenol-D. In other embodiments, the magnetostrictive
material may also be Cobalt, Metglas, Galfenol, rare earth-iron
film, or so forth.
The magnetic field acts as a force that affects the
magnetostrictive layers 202 and 206. The strain that results from
magnetostriction results in tension on layer 204. The magnetic
field sensor 200 may be connected to logic 210 that may utilize the
properties of the magnetic field sensor 200 to determine a magnetic
field 212 affecting the layers 202 and 206 and thereby layer 204.
For example, a sensed magnetic field may affect the
magnetostrictive material 208 of layers 202 and 206 to deform layer
204 thereby resulting in property changes to the layer 204. The
properties may represent frequency, resistance, conductance, or so
forth. The sensed changes in the properties may output as a signal
to the logic 210.
In one embodiment, logic 210 may be configured to receive a signal
from the layer 204 and process the signal to determine information
and data regarding a magnetic field detected by the magnetic field
sensor 200. For example, the logic 210 may include an
analog-to-digital converter and processor or ASIC for processing
the signals received according to one or more algorithms, set or
instructions or programming code, or processes that are herein
described or known in the art. The various components of the
magnetic field sensor 200 may be connected or communicate via pins,
wires, traces, leads, fiber optics, or other communications or
conductive components.
For example, the layer 204 may represent a quartz pressure gauge
with a vibration portion (e.g., beam). The force resulting from the
magnetic field affects the resonance frequency of the quartz
pressure gauge. The resulting frequency change may be utilized to
determine a magnitude and orientation of the sensed magnetic
field.
In one embodiment, the material properties for the layers 202-206
are as follows:
Layer 204 (e.g., Quartz gauge): a. Elastic modulus E.sub.Q=79 GPa,
density .rho..sub.Q=2650 kg/m.sup.3
Layers 202 and 206 (e.g., Terfenol-D): a. Elastic modulus
E.sub.T=35 GPa, density: .rho..sub.T=9250 kg/m.sup.3
In one embodiment, the deformation of the layer 204 (e.g., a
composite beam) may be analyzed utilizing the parallel axis
theorem, the area moment of inertia (I) for the composite beam in
the xx direction may calculated to be:
.times..times..times..times..times..times..function..times..times.
##EQU00001##
where w is the width of the composite beam 204, t.sub.Q the
thickness of the layer 204 (e.g., quartz crystal layer), t.sub.T
the thickness of the layers 202 and 206 (e.g., Terfenol-D). The
scaling factor n.sub.Q is defined as
##EQU00002## The linear density (m) of the composite beam of the
layer 204 may be given by:
m=2.rho..sub.Twt.sub.T+.rho..sub.Qwt.sub.Q=w(2.rho..sub.Tt.sub.T+.rho..su-
b.Qt.sub.Q) (Equation 2)
When the magnetostrictive layers 202 and 206 are subject to the
magnetic field 212, it produces strain as result of
magnetostriction, resulting in tension in the layer 204. Assuming
this tension is T, then the motion of the layer 204 may be
described by the following differential equation with the given
boundary conditions:
.times..times..differential..times..function..differential..times..differ-
ential..times..function..differential..times..differential..times..functio-
n..differential..times..function..function..differential..function..differ-
ential..times..differential..function..differential..times..times..times.
##EQU00003##
This assumes the two ends of the layer 204 are fixed. Equation 3
may be solved via Laplace Transform method or other means to show
that at resonance, the frequency of layer 204 obeys the following
frequency equation:
.function..OMEGA..times..times..function..times..function..OMEGA..times..-
times..function..times..function..OMEGA..times..times..times..OMEGA..omega-
..times..times..pi..times..times..times..times..times..times..times..times-
..times..times..times..times..times..times..OMEGA..times..times..times..ti-
mes..OMEGA..times..times. ##EQU00004##
Every parameter in the frequency Equation 4 is a known physical
parameter of the layer 204 except the tension T due to
magnetostriction. Once T is obtained, the magnetic sensor 200 or
interconnected device or logic 210 may directly calculate the
effect of magnetic field 212 on the resonance frequency to
determine the magnitude and direction of the magnetic field
212.
In order to calculate the amount of strain generated by the layers
202 and 206 in the presence of the magnetic field 212, the
relationship between strain the applied magnetic field may need to
be determined. In one embodiment, this is done utilizing the
"butterfly curve" associated with the magnetostrictive material as
shown in FIG. 4. The butterfly curve may be a transcendental plane
curved. Line 402 near the origin 404 is provided as a guide. The
slope of the line 402 is given by:
.DELTA..DELTA..times..times..apprxeq..times..times..times..times..mu..tim-
es..times. ##EQU00005##
Graph 400 illustrates a curve 406 for a magnetostrictive material,
such as Terfenol-D, with a 6.9 MP preload and a curve 408
illustrating no preload. In one embodiment, the slop of the line
402 is determined by measuring the change in the magnetic field and
the corresponding change in strain. For example, with a 6.9 MP
preload a 1 OE magnetic field may generate 13.5 microstrains in the
magnetostrictive material or layers. Using the relationship between
strain (.epsilon.), stress (.sigma.), and elastic modulus (E):
.DELTA..DELTA..sigma..times..times. ##EQU00006##
The magnetostrictive stress (.DELTA..sigma.) may be calculated by:
.DELTA..sigma.=E.sub.T.DELTA..epsilon.=13.5.times.10.sup.-6.times.35GPa/O-
e=472500Pa/Oe (Equation 7)
The total force due to magnetostriction may then given by
T=2t.sub.T.times.w.times..DELTA..sigma.
In one embodiment, the resonance frequency may be determined using
the frequency equation (Equation 4). The frequency equation may be
plotted out with the only unknown in the expression .OMEGA. as a
variable. Rewriting G(.OMEGA.) into G(z)=G(l.sup.2.OMEGA.), this
expression may be plotted out as shown in FIG. 5. The first root
G(z.sub.0)=G(l.sup.2.OMEGA..sub.0)=0 gives the fundamental
resonance frequency f.sub.0 according to Equation 4:
.times..pi..times..times..times..times..times. ##EQU00007##
A simple root-finding algorithm, such as Newton's algorithm may be
used to iteratively find the root G(z.sub.0)=0, starting with a
guess value for z.sub.o. The change in the frequency may be
utilized to determine the detected magnetic field. In one
embodiment, the various sensors or detectors may be calibrated
during manufacturing, in a laboratory, or in an environment.
Turning again to FIGS. 2-3, a composite beam of the layer 204 may
be placed in a magnetic field parallel to a long axis of the layer
204. Tension is generated by the layers 202 and 206. The tension
results in a slight shift of the root z.sub.o. For illustrative
purposes, the following physical parameters for the layer 204 are
used:
Physical dimensions: t.sub.Q=0.5 mm, t.sub.T=0.25 mm, w=2 mm, l=10
mm.
6.9 MPa Preload: T.sub.0=-6.9.times.10.sup.6
Pa.times.(2.times.t.sub.T.times.w+t.sub.q.times.w)=-13.8 Newton
Tension due to 1 Oe:
.DELTA.T=2.times.t.sub.T.times.w.times..DELTA..sigma.=472500.times.2.time-
s.t.sub.T.times.w=0.4725 Newton
With these sample parameters, the fundamental frequencies of the
composite beam of layer 204 with and without 1 Oe magnetic field
are:
TABLE-US-00001 Tension in the Composite beam Fundamental resonance
(Newtons) frequency (Hz) 6.9 MPa preload only -13.8 26648.43 6.9
MPa preload + -13.32 26654.26 1 Oe field .DELTA.f = 5.83 Hz
A 5 Hz shift in frequency out of 26 kHz may be a small change.
However, determining frequency measurement to high precision may be
performed utilizing logic. In another embodiment, multiple
composite beam or strain gauge sensors may be connected together.
One of the sensors may include magnetostrictive layers or materials
and one may not. Thus, a low frequency signal may be generated in
the presence of magnetic field 212, while such a frequency signal
is absent in the sensor without magnetostrictive materials absence
of magnetic field. The magnetic field sensor outputs a frequency
signal that may be proportional to the magnetic field strength.
In another embodiment, multiple layers of quartz crystal gauges and
magnetostrictive materials may be interlaced, stacked, or layered
to achieve amplification of the forces resulting from the magnetic
fields. As a result, the resulting forces upon the interlayered
strain gauges and magnetostrictive materials may be maximized for
an optimized reading of the magnetic field.
Turning now to FIGS. 5 and 6 showing a schematic, representation of
a magnetic field sensor array 500 and a graph 600 representing
vectors associated with the magnetic sensor array 500. In one
embodiment, the magnetic field sensor array 500 may include
multiple magnetic field sensors. For example, the magnetic field
sensor array 500 may include a set of three orthogonal sensors. A
magnetic field H 502 that is oriented in any arbitrary direction
may be decomposed into the three orthogonal orientations, H.sub.x
504, H.sub.y 506, and H.sub.z 508, (as shown by the graph 600)
along the three orthogonal sensor directions. As a result, the
magnetic field may be measured more definitely and decomposed into
distinct components along an x, y, and z axis of a sensor tool.
Specific actions, such as steering a tool or performing
avoidance,
Turning now to FIGS. 7 and 8 showing a magnetostriction graph 700
and a magnetic field sensor 802 in a magnetic field 708. In one
embodiment, the sensitivity of magnetostrictive materials utilized
in the magnetic field sensor 804 may be enhanced with a bias field.
Graph 700 illustrates a typical response of a magnetostrictive
material, such as Terfenol-D in the magnetic field 804. The graph
700 illustrates a saturation region 702, a linear region 704, and a
quadrature region 706.
Of the three regions, it may be desirable to operate the magnetic
field sensor 702 in the linear region 704 where the
magnetostrictive material has the largest change in
magnetostriction with the changing magnetic field 708. In one
embodiment, a pair of Helmholtz coils 802 may be utilized to
generate a uniform magnetic field along the axis of the magnetic
field sensor 802. The d.c. current fed into the Helmholtz coils 802
may be tuned to desired value so as to achieve the highest
sensitivity in the magnetostrictive material. For example, the
Helmholtz coils 802 may be integrated in a downhole or logging tool
that utilizes the magnetic field sensor 802. In another embodiment,
permanent magnets may be arranged to achieve the proper tuning.
Turning now to FIG. 9, showing a graph 900 illustrating a response
of a magnetic field sensor to a magnetic field in accordance with
an illustrative embodiment. When temperature and pressure are
known, the resonance frequency of a quartz crystal of the magnetic
field sensor shifts as a function of applied strain. Based on the
results in a section 1 902 the response may be described as:
.DELTA.f=F(.epsilon.) (Equation 10)
In the presence of a magnetic field H, in the linear region (after
bias), the strain due to the magnetostrictive layers is:
.epsilon.=cH (Equation 11)
Where c is a constant, H is the strength of the magnetic field
component along the long-axis of the quartz crystal. As a result,
the measurement of frequency shift yields the strain on the quartz
crystal of the magnetic field sensor, which leads to the magnetic
field.
In one embodiment, prior to field application, a quartz
crystal-Terfenol-D multilayer sensor may be calibrated with known
magnetic field which yields the resonance peak at f.sub.1 as
depicted in FIG. 9. Such a magnetic field may be the expected
average geomagnetic field at the field location or measurement
environment. In one embodiment, as the magnetic field sensor is
placed on a tool or bottomhole assembly inside a well and as the
orientation and magnitude of the local geomagnetic field changes,
the resonance frequencies of three orthogonal sensors may shift
accordingly. By analyzing the shift in resonance frequency
.DELTA.f, a determination of true magnetic North may be made.
In another embodiment, the difference of resonance frequencies
among the three orthogonal sensors may be monitored. When one of
the sensors has the maximum frequency shift while the other two
sensor experiences minimal shift, then the sensor with the maximal
shift is then substantially aligned with the local magnetic field
direction.
In yet another embodiment, the three orthogonal sensors may be
coupled into pairs or groups. The output of each pair will be the
beat frequency as result of the difference of the two sensors. At
much lower frequency, the beat frequency is easier to measure. The
beat frequency may also be utilized to enhance the resolution in
magnetic field measurements.
In addition to applications as geomagnetic positioning device, the
magnetic field sensor herein described may also be utilized to
detect any local magnetic anomalies, such as buried pipe, casing,
etc. Magnetic field sensing may be utilized and extremely important
for well interception. The magnetic field sensor may also be used
to detect the presence of magnetic ores.
The magnetic field sensors herein described may require quartz
resonant transducers. In one embodiment, a set of uncoated
reference oscillators may be required to get the highest precision
out of the sensor system. For example, a reference sensor may allow
for compensation based on some of the more difficult to match
shifts or offsets driven by temperature, pressure, and aging of the
underlying quartz oscillating crystals. The magnetic field sensors
may compensate for some of the deviations utilizing modeling, but
increased accuracy is most often achieved in referenced
systems.
In one embodiment, the magnetostrictive material may be applied
utilizing chemical vapor deposition, thin film deposition,
sputtering, atomic layer deposition, or other deposition processes.
In another embodiment, the magnetostrictive material may be
integrated with the material utilized to form the quartz crystal
gauge. Nano laminating may also be utilized followed by ion
homogenization.
One embodiment provides a system, method, and magnetic field
sensor. The magnetic field sensor may include a strain gauge. The
magnetic field sensor may further include one or more
magnetostrictive layers disposed upon the strain gauge. The
magnetostrictive layers may be configured to cause a displacement
of the strain gauge in response to sensing a magnetic field. The
magnetic field sensor may further include logic connected to the
strain gauge configured to determine parameters of the magnetic
field in response to sensing the magnetic field.
In another embodiment, the magnetic field sensor may include a
memory configured to store readings from the strain gauge. The
strain gauge may be a quartz crystal strain gauge. The parameters
may include any or all of an amplitude, orientation, or change of
the magnetic field. The magnetostrictive layers may be formed from
Terfenol-D. The magnetic field sensor may further include one or
more arrays of strain gauges including the strain gauge. Each of
the one or more arrays of strain gauges may include at least three
orthogonal he position strain gauges to sense the amplitude and
orientation of the magnetic field. In amplitude and orientation of
one or more magnetic fields including the magnetic field may be
communicated to a remote device. The strain gauge may include a
number of gauge layers interlayered with the one or more layers of
magnetostrictive layers. The magnetic field sensor may be
integrated in a downhole tool for natural resource exploration.
Another embodiment provides a magnetic field sensor. The magnetic
field sensor may include an array of court strain gauges. The
magnetic field sensor may further include one or more
magnetostrictive layers disposed upon the array of court strain
gauges. The magnetostrictive layers deform the array of court
strain gauges in response to sensing and magnetic field. The
magnetic field sensor may further include logic connected to the
array of court strain gauges that determines parameters of the
magnetic field in response to the magnetostrictive layers sensing
the magnetic field.
In another embodiment, the array of court strain gauges may include
at least three orthogonally placed quartz strain gauges. The array
of court strain gauges may generate signals that represent
resonance frequencies of each of the quartz strain gauges that are
utilized to determine the parameters including at least an
amplitude and an orientation of the magnetic field. The array of
quartz strain gauges may include at least two sets of three
orthogonally play positioned quartz strain gauges. The one or more
magnetostrictive layers may be interlayered with each of the array
of quartz strain gauges.
Yet another embodiment includes a method for measuring a magnetic
field. A downhole tool including a magnetic field sensor may be
positioned in a wellbore. A signal may be generated utilizing a
gauge including one or more layers of magnetostrictive materials in
response to sensing the magnetic field. The signal is processed to
determine parameters of the magnetic field.
In another embodiment, the magnetic field sensor may include a
quartz strain gauge coated in the one or more layers of the
magnetostrictive materials. The parameters may include an amplitude
and an orientation of the magnetic field. The deformation of the
quartz strain gauge is determined utilizing the parallel axis
theorem. The signal represents a resonance frequency of a strain
gauge of the magnetic field sensor. The magnetic field sensor is
utilized to determine proximity to a wellbore component.
In the previous embodiments, reference is made to the accompanying
drawings that form a part hereof. These embodiments are described
in sufficient detail to enable those skilled in the art to practice
the invention, and it is understood that other embodiments may be
utilized and that logical, structural, mechanical, electrical, and
chemical changes may be made without departing from the scope of
the invention. To avoid detail not necessary to enable those
skilled in the art to practice the embodiments described herein,
the description may omit certain information known to those skilled
in the art. The detailed description is, therefore, not to be taken
in a limiting sense, and the scope of the illustrative embodiments
is defined only by the appended claims.
In the drawings and description that are included, the drawing
figures are not necessarily to scale. Certain features of the
invention may be exaggerated in scale or in somewhat schematic form
and some details of conventional elements may not be shown in the
interest of clarity and conciseness.
The previous detailed description is of a small number of
embodiments for implementing the invention and is not intended to
be limiting in scope. The following claims set forth a number of
the embodiments of the invention disclosed with greater
particularity.
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